1. Field of the Invention
The present invention relates to an air bag system for extending an air bag at the time of a collision of a vehicle to protect a passenger and, more particularly, to a jointing structure between a casing and a door of the air bag system.
2. Description of the Related Art
In a passenger's air bag system, there are attached to a casing (which may also be called a "container") not only an air bag and an inflater but also a door covering an opening of the casing. The door may also be called a "cover door" or a "deployment door". At the time of a collision of a vehicle, the inflater is energized to extend the air bag so that the door is opened into the cabin by the air bag being extended until the air bag is fully extended into the cabin.
The schematic construction and operation of a passenger's air bag system of the prior art will be described with reference to FIGS. 8 to 11.
FIG. 8 is a schematic section showing the passenger's air bag system of the prior art, and FIG. 9 is a section taken along line IX--IX of FIG. 8. This passenger's air bag system 10 contains an air bag 14 in a folded state in a casing 12. In the casing 12, there is disposed an inflater 16 for extending the air bag 14. The casing 12 has an opening at a front side thereof (or its upper side, as seen from FIG. 8) which is opened toward a vehicle cabin. The opening is covered with a door 18, which is constructed by mounting a metallic back plate 18b on the back of a door body 18a made of a synthetic resin. A reinforcing member such as mesh is inserted, if necessary, into the door body 18a.
The back plate 18b has its one side raised generally vertically of the door 18 to form a leg portion 20, which is fixed on the casing 12 by means of bolts 22. Incidentally, these bolts 22 may be replaced by other fixtures such as rivets. By these bolts or rivets, the air bag 14 is fixed together with the leg portion 20 in the casing 12.
In the back plate 18b at the opposite side of the leg portion 20, there is fixed a joint 24, through which the door 18 is jointed to the casing 12. Designated at numeral 26 are bolts (although may be replaced by rivets) for fixing the joint 24 on the casing 12. These bolts 28 fix the air bag 14 in the casing 12.
The joint 24 is formed with a neck portion 28 , at which the joint 24 is broken, when the door 18 is opened by operating the air bag system, to allow the door 18 to turn in its opening direction.
If the vehicle carrying the passenger's air bag system thus constructed meets an emergency such as a collision, the inflater 16 discharges gases to extend the air bag 14 abruptly. At this time , the air bag 14 pushes the door 18 so that the neck portion 28 is broken at first, as shown in FIG. 10. Then, the door 18 is turned in the opening direction about its leg portion 20, as indicated by arrow A in FIG. 11. Thus, the air bag 14 is fully extended into the cabin, as indicated by arrow B.
The passenger's air bag system of the prior art has its neck portion 28 broken, after the air bag system is energized, and a residual portion 30 is produced on the door 18. The portion 30 protrudes considerably from the inner face of the door 18. The air bag 14 makes contact with the residual portion 30 when the bag is extending into the cabin. The residual portion 30 has its leading end portions so sharply corrugated that it will damage the air bag 14. Thus, the air bag 14 is required to be fabricated with a strong and tough cloth for eliminating any risk of being broken even if the air bag 14 slides on the residual portion 30. The strong and tough cloth raises a prime cost of the air bag 14.